1. Field of the Invention
The present invention relates to an automatic focus adjusting apparatus particularly for a camera.
2. Description of the Prior Art
Until now, proposals have been made for various kinds of automatic focus adjusting apparatus. Light projected by a light projector and reflected from the object is detected by a light sensor to adjust the focus. Such apparatus are accurate when the object is close. However, when the object is far away, the energy of the light projected by the light projector and reflected on the object is too small for the peak value to be detected accurately enough for an accurate focus adjustment.
To some extent, this difficulty can be overcome to some extent by using a large light projector or a large power source to increase the output of the light projector by using a large condenser lens to increase the sensing accuracy of the apparatus. However, this makes the apparatus quite large so that its lack of portability makes it inconvenient.
In a conventional apparatus, when the object is within a predetermined range, accurate focusing is possible while, on the other hand, when the object is beyond that range, accurate focusing is not possible due to the weak reflected light.
A purpose of the present invention is to offer a simple automatic focus adjusting apparatus by means of which an accurate focus adjustment can be obtained from the close distance to a distance beyond the predetermined range such as a range embracing the hyperfocal distance.
Another purpose of the present invention is to offer a simple automatic focus adjusting apparatus by means of which an accurate focus adjustment can be obtained from close up to .infin..